Urban American Indian and Alaskan Natives May Have Lower Survival Rates Following Invasive Prostate and Breast Cancers

Key Points

As enrollees of the same comprehensive health plan, participants of the study had approximately equal access for both cancer treatment and preventative services. However, American Indian and Alaskan Natives (AIAN) had a somewhat higher comorbidity burden as compared to non-Hispanic whites.

“The AIAN population has a unique history of social, environmental, and cultural injustices that have impacted health. As a result, many of these long-term exposures have resulted in an unequal contemporary burden of comorbid health conditions,” explained researchers.

The AIAN community had an 87% increased risk for prostate cancer–specific mortality and a 47% increased risk for all-cause mortality following invasive breast cancer, after controlling for patient factors, disease characteristics, and comorbidity status.

Compared with the non-Hispanic white (NHW) population, the urban American Indian and Alaskan Native (AIAN) community was more likely to have lower survival rates following invasive prostate and breast cancer, according to a new study by Emerson et al in Cancer Research.

Previous AIAN data regarding cancer incidence and mortality are linked with the Indian Health Service (IHS); however, access to IHS facilities for the majority of AIANs is limited, as IHS clinics and hospitals are located near reservation lands, Mr. Emerson explained. Additionally, only members of federally recognized AIAN tribes qualify for treatment by the IHS. Altogether, it is estimated that up to 80% of the AIAN population cannot utilize IHS services, resulting in data acquisition that is not representative of the entire cohort, he said.

Study Findings

This study analyzed data from 582 AIAN and 82,696 NHW enrollees of Kaiser Permanente Northern California (KPNC), a health-care system that covers roughly one-third of people living in the Bay Area and Central Valley in California. Participants were diagnosed with primary invasive breast, prostate, lung, or colorectal cancer between January 1997 and December 2015. As enrollees of the same comprehensive health plan, participants of this study had approximately equal access for both cancer treatment and preventative services. However, AIANs had a somewhat higher comorbidity burden as compared to NHWs.

“The AIAN population has a unique history of social, environmental, and cultural injustices that have impacted health,” noted Emerson. “As a result, many of these long-term exposures have resulted in an unequal contemporary burden of comorbid health conditions.”

In addition to comorbidity burden, senior author Laurel A. Habel, PhD, Associate Director for Cancer Research at KPNC, and colleagues compared cancer survival between the AIAN and NHW populations. They found that the AIAN community had an 87% increased risk for prostate cancer–specific mortality and a 47% increased risk for all-cause mortality following invasive breast cancer, after controlling for patient factors, disease characteristics, and comorbidity status. Additional adjustment for income did not significantly change the outcomes. Researchers did not observe higher overall or cancer-specific mortality for AIAN individuals with lung or colorectal cancer.

Commentary

“Our results suggest that factors other than health insurance and income may play a role in the survival differences observed for breast and prostate cancer,” said Mr. Emerson. “These factors could include differences in tumor biology or differences in aspects of treatment, such as adherence.”

Future studies on the tumor biology of cancers in the AIAN population and on adherence to cancer treatments could help better understand and address the disparities, Emerson said.

Limitations of the study include an inability to control for quality of care, adherence, or lifestyle factors that may vary across racial subgroups.

“The electronic health records do not have data on some lifestyles and behaviors that may have influenced cancer outcomes,” Dr. Habel noted.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.